Environmental stress during grain filling may affect wheat protein composition, thus influencing its final quality. A proteomic approach was used to evaluate changes in storage protein composition under water stress of two Italian durum wheat (Triticum turgidum ssp. durum) cultivars, Ciccio and Svevo. The high-molecular-weight glutenin region increased progressively in both cultivars and under two water regimens. The L48â35 region, corresponding to low-molecular-weight (LMW) glutenin subunits, increased slightly during grain development and decreased under water stress in both cultivars. In particular, an s-type LMW related to superior technological quality was down-expressed in the earlyâmid period in Svevo and in the midâlate period in Ciccio. Finally, the L<35 region, corresponding to gliadin-like proteins, decreased slightly during grain development and increased under stress in both cultivars. Several Î±-gliadins, associated with immunological potential, increased their expression under water stress, especially in Svevo in the earlyâmid stage of grain filling.